1. Field of the Invention
The present invention relates to a bearing positioning member for a spindle motor.
2. Description of Related Art
A typical conventional bearing positioning member for a spindle motor or heat dissipating fan is disclosed in, as shown in FIG. 9. The motor includes a washer 101, a compression spring 102 that is substantially cylindrical, a retainer 21, and a positioning sleeve 301. The washer 101 and the compression spring 102 are mounted between a rotor 10 and a ball bearing 20. The retainer 21 is mounted to a bottom of another ball bearing 20′, and the positioning sleeve 301 is tightly engaged with an inner periphery of an axle tube 30. When the rotor 10 moves axially toward the bearing 20 during operation, the compression spring 102 exerts a force to the rotor 10, assuring a gap between the rotor 10 and the bearing 20. The positioning sleeve 301 maintains the fixed positional relationship between the two bearings 20 and 20′ in the axle tube 30 and absorbs the vibrations generated during operation to thereby reduce noise.
Since the washer 101 and the compression spring 102 having a simple structure and a low cost, they are widely used in spindle motors and heat dissipating fans. However, the compression spring 102 supports the rotor 10 by a small area and thus fails to provide a reliable, stable support for the rotor 10. Further, the axial compression of the compression spring 102 is limited, as the coils of the compression spring 102 are stacked upon one another in the axial direction. Further, the coils of the compression spring 102 that are stacked upon one another and press against one another often cause distortion and deformation of the compression spring 102 in the radial direction while the compression spring 102 is compressed. Further, when the rotor 10 turns, the washer 101 that is in contact with an inner race 20a and the outer race 20b of the ball bearing 20 at the same time is apt to wear. Further, it is not easy to accurately mount the positioning sleeve 301 into the axle tube 30. Conclusively, the bearing positioning structure of this conventional motor could not meet the end of providing a balanced rotation for the rotor of a spindle motor.